Continuously variable transmission

ABSTRACT

Traction planets and traction rings can be operationally coupled to a planetary gearset to provide a continuously variable transmission (CVT). The CVT can be used in a bicycle. In one embodiment, the CVT is mounted on the frame of the bicycle at a location forward of the rear wheel hub of the bicycle. In one embodiment, the CVT is mounted on and supported by members of the bicycle frame such that the CVT is coaxial with the crankshaft of the bicycle. The crankshaft is configured to drive elements of the planetary gearset, which are configured to operationally drive the traction rings and the traction planets. Inventive component and subassemblies for such a CVT are disclosed. A shifting mechanism includes a plurality of pivot arms arranged to pivot about the centers of the traction planets as a shift pin hub moves axially.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/263,900, filed Apr. 28, 2014 and scheduled to issue on May 17, 2016as U.S. Pat. No. 9,341,246, which is a continuation of U.S. patentapplication Ser. No. 12/039,590, filed Feb. 28, 2008 and issued as U.S.Pat. No. 8,708,360 on Apr. 29, 2014, which is a continuation of U.S.patent application Ser. No. 11/562,317, filed on Nov. 21, 2006, whichclaims benefit of U.S. Provisional Patent Application No. 60/738,865,filed on Nov. 22, 2005. The disclosures of all of the above-referencedprior applications, publications, and patents are considered part of thedisclosure of this application, and are incorporated by reference hereinin their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The field of the invention relates generally to transmissions, and moreparticularly to continuously variable transmissions (CVTs).

Description of the Related Art

Embodiments of the CVTs disclosed here can be used in any machine,device, vehicle, etc., where it is desired to adjust the ratio of inputspeed to output speed. A bicycle is one such application. The drivetrainof a bicycle typically consists of pedals coupled to cranks for drivinga crankshaft, which is received in, and supported by, frame members ofthe bicycle. The crankshaft is coupled to a sprocket that transferspower to the rear wheel of the bicycle by a chain. A cog at the rearwheel receives power from the chain and is adapted to interface with therear wheel hub for driving the rear wheel of the bicycle. Some bicyclesare provided with internally geared rear hubs, where a set of gears isarranged to receive power from the cog and drive the rear wheel. In someapplications, a bicycle is provided with a CVT at the rear hub to drivethe rear wheel.

However, there remains an unfulfilled need for a CVT that is receivedand supported by the frame members of the bicycle at a location forwardof the rear wheel or rear wheel hub. The embodiments of the CVTsdisclosed here address this and other needs in the field of continuouslyvariable transmissions.

SUMMARY OF THE INVENTION

The systems and methods described herein have several features, nosingle one of which is solely responsible for the overall desirableattributes. Without limiting the scope as expressed by the claims thatfollow, the more prominent features of certain embodiments of theinvention will now be discussed briefly. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description of Certain Inventive Embodiments,” one willunderstand how the features of the systems and methods provide severaladvantages over related traditional systems and methods.

One aspect of the invention relates to a bicycle having a plurality ofbicycle frame members, a crankshaft operationally coupled to one or morecranks of the bicycle, and a continuously variable transmission (CVT)coaxially coupled with, and coaxially mounted about, the crankshaft.

Another aspect of the invention is addressed to a bicycle having acrankshaft coupled to a rotatable planetary gear set carrier coupled,and a plurality of planet gears coupled to said carrier. A ring gear,rotationally constrained, can be coupled to the planet gears, which canbe coupled to a sun gear coupled. A first traction ring is operationallycoupled to the sun gear, and a plurality of traction planets are coupledto the traction ring. A second traction ring is coupled to the tractionplanets. Power is transferred sequentially from the crankshaft to theplanetary gear set carrier, to the planetary gears, to the sun gear, tothe first traction ring, to the traction planets, and to the secondtraction ring. In another embodiment, the crankshaft is additionallycoupled to a cage that is adapted to support the traction planetsaxially and radially and to transfer power to the traction planets.

Yet another aspect of the invention concerns a bicycle transmissionhaving a planetary gear set configured for coupling to a crankshaft of abicycle and to be mounted coaxially about the crankshaft. The bicycletransmission can further have a continuously variable variator coupledto the planetary gearset configured to be mounted coaxially about thecrankshaft.

Still another aspect of the invention is directed to a shift screw and ashift pin hub for facilitating the adjustment of a transmission ratio.In another regard, the invention relates to a device for actuating anaxial translation of an idler or traction sun as the transmission ratiois adjusted. In one embodiment, the traction sun actuation deviceincludes a plurality of cam rollers configured to interface with a camsurface of a pivot arm. Another aspect of the invention covers the pivotarms having an integral cam surface for facilitating the axialtranslation of the traction sun.

In one aspect the invention is directed to a cage for a transmission.The cage has a plurality of splines for engaging corresponding splinesof a transmission housing. The cage can further can a plurality of slotswith skew roller reaction surfaces.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is schematic cross-section of continuously variable transmission(CVT) implemented on the frame of a bicycle.

FIG. 2 is a schematic cross-section of yet another embodiment of a CVTimplemented on the frame of a bicycle.

FIG. 3 is a perspective view of still another embodiment of a CVT thatcan be implemented, among other things, on the frame (such as the bottombracket) of a bicycle.

FIG. 4A is a perspective, cross-sectional view of the transmission ofFIG. 3.

FIG. 4B is a cross-sectional view of the transmission of FIG. 3.

FIG. 4C is a partial, exploded view of certain assemblies and componentsof the transmission of FIG. 3.

FIG. 4D is a partial, exploded view of certain assemblies and componentsof the transmission of FIG. 3.

FIG. 5 is a perspective, partially exploded view of certain componentsof a housing for the transmission of FIG. 3.

FIG. 6A is a perspective view of a planetary gear set carrier that canbe used with the transmission of FIG. 3.

FIG. 6B is an elevational side view of the planetary gear set carrier ofFIG. 6A.

FIG. 7A is a perspective view of a cage that can be used with thetransmission of FIG. 3.

FIG. 7B is a perspective view of a cage component of the cage of FIG.7A.

FIG. 7C is a second perspective view of the cage component of FIG. 7B.

FIG. 8A is a perspective view of a planet-pivot-arm assembly that can beused with the transmission of FIG. 3.

FIG. 8B is a cross-sectional view of the planet-pivot-arm assembly ofFigure A.

FIG. 9 is a perspective view of a traction ring and clamping forcegeneration assembly that can be used with the transmission of FIG. 3.

FIG. 10A is a perspective view of an input driver that can be used withthe transmission of FIG. 3.

FIG. 10B is another perspective view of the input driver of FIG. 10A.

FIG. 10C is a cross-sectional view of the input driver of FIG. 10A.

FIG. 10D is a perspective view of an output driver that can be used withthe transmission of FIG. 3.

FIG. 10E is another perspective view of an output driver that can beused with the transmission of FIG. 3.

FIG. 10F is a cross-sectional view the output driver of FIG. 10D.

FIG. 11A is a perspective view of a shift screw that can be used with ashifting actuator of the transmission of FIG. 3.

FIG. 11B is a cross-sectional view of the shift screw of FIG. 11A.

FIG. 12A is a perspective view of a shift pin hub that can be used witha shifting actuator of the transmission of FIG. 3.

FIG. 12B is a cross-sectional view of the shift pin hub of FIG. 12A.

FIG. 13A is a detail view A of FIG. 4B showing a traction sun actuationdevice that can be used with the transmission of FIG. 3.

FIG. 13B is a perspective view of the traction sun actuation device ofFIG. 13A.

FIG. 13C is a side elevational view of traction sun actuation device ofFIG. 13B.

FIG. 13D is an exploded view of the traction sun actuation device ofFIG. 13B.

FIG. 14A is a perspective view of certain components of the CVT of FIG.3 showing a shifting actuator for the CVT.

FIG. 14B is second perspective view of certain components shown in FIG.14A.

FIG. 14C is a cross-sectional view of the components shown in FIG. 14A.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

Reference will now be made in detail to the present embodiments(s)(exemplary embodiments) of the invention, an example(s) of which is(are) illustrated in the accompanying drawings. Wherever possible, thesame reference numbers will be used throughout the drawings to refer tothe same or like parts (elements).

The CVT embodiments described here are generally related to those of thetype disclosed in U.S. Pat. Nos. 6,241,636; 6,419,608; 6,689,012; and7,011,600. The entire disclosure of each of these patents is herebyincorporated herein by reference. Additionally, U.S. patent applicationSer. No. 10/788,736 (now U.S. Pat. No. 7,011,600) was included asAppendix A of the provisional application from which this applicationclaims priority. The disclosure of U.S. patent application Ser. No.11/543,311, filed Oct. 3, 2006, is hereby incorporated by referenceherein in its entirety.

The preferred embodiments will now be described with reference to theaccompanying figures, wherein like numerals refer to like elementsthroughout. The terminology used in the description presented herein isnot intended to be interpreted in any limited or restrictive mannersimply because it is being utilized in conjunction with a detaileddescription of certain specific embodiments of the invention.Furthermore, embodiments of the invention may include several novelfeatures, no single one of which is solely responsible for its desirableattributes or which is essential to practicing the inventions hereindescribed.

As used here, the terms “operationally connected,” “operationallycoupled”, “operationally linked”, “operably connected”, “operablycoupled”, “operably linked,” and like terms, refer to a relationship(mechanical, linkage, coupling, etc.) between elements whereby operationof one element results in a corresponding, following, or simultaneousoperation or actuation of a second element. It is noted that in usingsaid terms to describe inventive embodiments, specific structures ormechanisms that link or couple the elements are typically described.However, unless otherwise specifically stated, when one of said terms isused, the term indicates that the actual linkage or coupling may take avariety of forms, which in certain instances will be obvious to a personof ordinary skill in the relevant technology.

For description purposes, the term “radial” is used here to indicate adirection or position that is perpendicular relative to a longitudinalaxis of a transmission or variator. The term “axial” as used here refersto a direction or position along an axis that is parallel to a main orlongitudinal axis of a transmission or variator. For clarity andconciseness, at times similar components labeled.

FIG. 1 illustrates one embodiment of a bicycle transmission 100 mountedin a bicycle frame 102 rather than the rear hub of the bicycle (notshown). The illustrated embodiment integrates a support structure 104 ofthe transmission into the frame 102 of the bicycle. The major componentsof the transmission 100 include a variator 106, a planetary gear set 110and a support structure 104. The planetary gear set 110 of theillustrated embodiment includes a central sun gear 112, a set of planetgears 114 that orbit and surround the sun gear 112, a set of planetgears 114 that orbit and surround the sun gear 112, and a ring gear 116that surrounds the set of planer gears 114. In FIG. 1, a dashed circleis used to better illustrate the location of the ring gear 116 that, inthe illustrated embodiment, is integrated with the support structure104. Each of the planet gears 114 rotates about a respective planetshaft 118, and a planet carrier 120 supports the planet shafts 118. Inthe exemplary embodiment of FIG. 1, the planet gears 114 are compoundplanetary gears.

As described in the embodiments described in U.S. Pat. No. 7,011,600,the variator 106 of the illustrated embodiment includes an input ring124, an output ring 126, and a set of planet balls 130 in contact with,and between, the input ring 124 and the output ring 126. An idler 132 isplaced between, and in contact with, the planet balls 130, and isanalogous to the sun gear 112 of the planetary gear set 110. Thevariator 106 operates as illustrated and described in U.S. Pat. No.7,011,600.

Cranks 140 of a bicycle provide torque input into the planet carrier120. The planet carrier 120 rotates the planet gears 114 about the sungear 112. The ring gear 116 is fixed and the planet gears 114 drive thesun gear 112. The ring gear 116 is fixed, and the planet gears 114 drivethe sun gear 112. The planet carrier 120 is connected to the cage 142 ofthe variator 106. The sun gear 112 is connected to the input ring 124via a cam loader 144, a set of bearings 146 and ramps 148 that generatesaxial force that is proportional to the amount of torque applied,although any axial force generating mechanism described in U.S. Pat. No.7,011,600 or known or described in previous publications can be used.Therefore, in the illustrated embodiment, torque is supplied to thevariator 106 from both the sun gear 112, via the input ring 124, and thecarrier 120, via the cage 142. The variator 106 takes and sums the twotorque inputs and varies the output speed to the output ring 126 and outvia an output sprocket 150. The illustrated embodiment includes anoptional reaction sleeve 152 to react the axial force generated as wellas a thrust bearing 154 for reacting the axial thrust generated to clampthe input ring 124 and the output ring 126 to the planet balls 130.

In the embodiment illustrated in FIG. 2, a second embodiment isillustrated that also utilizes the planetary gear set 110 as an input tothe variator 106. In this embodiment, torque again is applied from thecranks 140 to the carrier 120 and output through the sun gear 112. Inthis embodiment, however, the carrier 120 is not attached to the cage142 and, therefore, torque is only input to the variator 106 through theinput ring 124 while the cage 142 is fixed to the frame 102.

An alternative transmission 300 will now be described with reference toFIGS. 3-13D. The transmission 300 can use components similar to thosedescribed above with reference to the embodiments of the transmission100. However, the use of a similar or identical reference name for acomponent does not necessarily introduce into an embodiment (or aspectof the embodiment) any characterizations associated with a previouslydescribed embodiment.

FIG. 3 is a perspective view of the transmission 300. In one embodiment(in a bicycle application, for example), power can be provided to thetransmission 300 via cranks 350, and power can be delivered out of thetransmission 300 via a sprocket 348. The transmission 300 can include acentral hub shell 390 that, along with end caps 302 and 346, forms ahousing 345 for most of the components of the transmission 300. In oneembodiment, the housing 345 can be configured to be implemented on abicycle frame, such as in the bottom bracket of the bicycle, forexample. However, the transmission 300 can be used in any machine orvehicle where it is desired to adjust the ratio of input speed to outputspeed, or vice versa. That is, although various embodiments and featuresof the transmissions described herein are discussed with reference to abicycle application, a person of ordinary skill in the relevant art willreadily recognize modifications of and to the transmission 300, andfeatures thereof, that can be used in any vehicle, machine, or devicethat uses a transmission to adjust the ratio of input to output speeds.

Referencing FIGS. 4A-4D now, an exemplary embodiment of certainassemblies and components of the transmission 300 will now be described.In one embodiment, the transmission 300 can include a set ofplanet-pivot-arm assemblies 410 positioned between an input tractionring 330 and an output traction ring 336. The planet-pivot-armassemblies 410 can include an array of traction planets 332 in contactwith the input traction ring 330, the output traction ring 336, and atraction sun 333. The transmission 300 can include an input driver 326for operationally driving the input traction ring 330. The outputtraction ring 336 is configured to operationally driver the outputdriver 340. Preferably, the transmission 300 includes an input load cam328 positioned between the input driver 326 and the traction ring 330.The transmission preferably also includes an output load cam 338 locatedbetween the output traction ring 336 and the output driver 340. In theembodiment illustrated, a cage 356 is provided to support and guide theplanet-pivot-arm assemblies 410, as well as to provide stiffness and/orrigidity to the transmission 300. It should be noted that the previousrecitation of components of the transmission 300 can be expanded orreduced, and that enumerated members can be combined together andcontinue to perform their intended functions, without departing from thescope of present invention.

The cranks 350 are coupled to provide torque to a crank shaft or centralshaft 360, which is generally positioned and supported in the housing345 by bearings 395. The central shaft 360 can also be configured toprovide radial and axial support for certain assemblies of thetransmission 300. For purposes of description, the central shaft 360defines a longitudinal axis of the transmission 300 that will serve as areference point for describing the location and/or motion of othercomponents of the transmission 300. As used here, the terms “axial,”“axially,” “lateral,” “laterally,” refer to a position or direction thatis coaxial or parallel with the longitudinal axis defined by the centralshaft 360. The terms “radial” and “radially” refer to locations ordirections that extend perpendicularly from the longitudinal axis.

In one embodiment, the cranks 350 couple to a first stage planetary gearset via the central shaft 360. The first stage planetary gear setincludes sun gear 312, compound planetary gears 310, carrier 320, andring gear 316. The central shaft 360 couples to the ring gear 316. Thecarrier 320 is configured to receive and support, on planetary gearaxles 318, the compound planetary gears 310. In one embodiment, thecarrier 320 is rotationally and axially fixed, and can be part of (orattached to) the housing 345.

The ring gear 316 drives the compound planetary gears 310, which orbitaround and drive the sun gear 312. The input driver 326 is coupled toand receives torque from the sun gear 312. The input driver 326 deliverstorque via the input load cam 328 to the input traction ring 330, whichtransfers torque to the planet-pivot-arm assemblies 410. The outputdriver 340 receives torque from the planet-pivot-arm assemblies 410 viathe output traction ring 340 and output load cam 338. The output driver340 is coupled to and delivers torque to the sprocket 348. Although asprocket is used in this example, other embodiments of the transmission300 can use a pulley, a freewheel, a cog, etc.

In some embodiments, the input traction ring 330 and the output tractionring 340 are substantially similar. A traction ring 330, 340 preferablyincludes a traction surface for transmitting torque through frictionalor hydroelastodynamic contact with the traction planets 332. In someembodiments, a traction ring 330, 340 can include ramps that form partof a load cam assembly (see FIG. 10). The traction surface of thetraction ring 330, 340 can be inclined at about 45 degrees fromvertical, which in this case refers to a plane surface extendingradially.

A cage 356 includes an input cage 352 and an output cage 354 (see FIGS.7A-7C), and circumscribes and supports the planet-pivot-arm assemblies410, as depicted in FIGS. 4A-4D. A planet-pivot-arm assembly 410 caninclude a traction planet 332. The traction planets 332 are in contactwith and are radially supported by the traction sun 333. An exemplaryplanet-pivot-arm assembly 410 is depicted in FIG. 9. The traction sun333 can be a generally cylindrical tube. In some embodiments, thetraction sun 333 has a generally constant outer diameter; however, inother embodiments the outer diameter is not constant. The outer diametermay be smaller at the center portion than at the ends, or may be largerat the center and smaller at the ends. In other embodiments, the outerdiameter is larger at one end than at the other and the change betweenthe two ends may be linear or non-linear depending on shift speed andtorque requirements.

A planet-pivot-arm assembly 410 can have pivot arms 380, which can beoperationally coupled to a traction sun actuation device 382 (see FIGS.4B and 13A-13D). As will be discussed further below, the traction sunactuation device 382 can be used to translate axially the traction sun333 when the speed ratio of the transmission 300 is adjusted. The pivotarms 380 can be coupled to a shift pin hub 374 via hub pin fingers 376(see FIG. 13A) and shift pins (not shown). The shift pin hub 374 can beused to actuate the planet-pivot-arm assembly 410 in response to ashifting input. Shifting, or adjustment of the speed ratio, of thetransmission will be further described below with reference to FIGS.11A-12B.

To handle axial reaction forces and provide a rolling contact betweenmoving and stationary members of the CVT 300, thrust bearings can beprovide on either or both of the input and output ends of the CVT 300.At the input side, generally referring to the area where the centralshaft 360 couples to the ring gear 316, an input thrust bearing islocated between the stationary, first stage planetary carrier 320 andthe input driver 326. The input thrust bearing, in the embodimentillustrated in FIG. 4, includes an input bearing race 322 that isreceived and supported in a recess of the carrier 320. The input thrustbearing also has a set of rollers 324 that can be positioned andsupported by a roller retainer. The rollers 324 can be balls, barreledrollers, asymmetrical rollers or any other type of rollers. In oneembodiment, the input driver 326 is provided with an integral bearingrace that cooperates with the rollers 324 and the input bearing race 322to complete the input thrust bearing.

On the output side, generally referring to the area where the outputdriver 340 is located, an output thrust bearing can be positionedbetween the output driver 340 and the end cap 346, which can have arecess for receiving and support an output bearing race 344. Thus, inthis embodiment, the end cap 346 helps to react the axial forces thatarise in the transmission 300. The bearing races 322, 344 can be made ofvarious bearing race materials such as steel, bearing steel, ceramic orany other material suitable for bearing races. The output thrust bearingincludes a set of rollers 342 positioned and supported in rollerretainer. In one embodiment, the output driver 340 can have an integralbearing race that cooperates with the output bearing race 344 and therollers 342 to complete the output thrust bearing.

Referencing FIG. 5 now, in one embodiment, the housing 345 includes acentral hub shell 390, an input end cap 302, and an output end cap 346.In one embodiment, the end caps 302, 346 fasten to the central hub shell390 with fasteners (not shown); however, the ends cap 302, 346 can alsothread into, or can otherwise be attached to the central hub shell 390.The central hub shell 390 can be provided with internal splines 392formed integral with the inside of the hub shell 390 to engage withcomplimentary splines 925 of the cage 356. The end caps 302, 346 aregenerally flat discs, although either or both can have a curved shape orother configuration. As shown in FIG. 5, the end cap 346 can be providedwith a recess 1405 adapted to receive and support the output bearingrace 344. The central bores of the end caps 302, 346 can be adapted toreceive the bearings 395 for providing positioning and rolling contactwith respect to other components of the transmission 300. The end caps302 and 346 can be made of, for example, aluminum, titanium, steel, highstrength thermoplastics, or thermoset plastics. Depending on theembodiment, the end caps 302 and 346 are preferably made of a materialsuitable to provide rigidity and stiffness to the transmission 300, aswell as to react the axial forces that arise in the transmission 300during operation.

Turning to FIGS. 6A-6B now, the first stage planetary carrier 320 can beadapted by machining, or formed as an integral piece, to be capable ofaxially and radially supporting the compound planetary gears 310. Thecarrier 320 includes bore holes 605 adapted to secure and receive theplanetary shafts 318. The carrier 320 can include cavities 610 and 615formed integral with the carrier 320 to receive the compound planetarygears 310. A central bore 620 of the carrier 320 can be configured toreceive a bearing 396, which serves to locate, and provide a rollinginterface for, the input driver 326 (see FIG. 4B, for example). Aspreviously mentioned, in some embodiments that carrier 320 can beconfigured to form part of the housing 345 and/or to receive and supportthe bearing race 322.

Passing to FIGS. 7A-7C, a cage 356 can have two halves, input cage half352 and input cage half 354. In one embodiment, the cage halves 352, 354can be substantially similar. Hence, the cage halves 352, 354 can beinterchangeable. Is some embodiments, the cage 356 is shaped to providea stationary, reaction support structure for the pivot arms 380; thatis, the cage 356 is configured to provide the angular alignment (aboutthe longitudinal axis of the central shaft 360) for the pivot arms 380(and consequently, the traction planet axles 334) as the pivot arms 380pivot radially inward and outward about the traction planets 332 duringshifting of the transmission ratio.

In one embodiment, the slots 915 of the cage 356 guide theplanet-pivot-arm assemblies 410 along skew surfaces 910 through contactwith the skew rollers 1220. The skew surfaces 910 provide reactionsurfaces for the skew rollers 1220 as the planet-pivot-arm assemblies410 pivot or tilt in slot 915 when the transmission ratio of the CVT 300is adjusted. In some embodiments, the corresponding slots of cage halves352, 354 are offset slightly in the angular direction, relative to oneanother, to reduce potential deleterious effects on shifting, forexample, that can be caused by skewing (relative to a lateral axis) ofthe traction planet axles 334 (see FIG. 9A).

Turning to FIGS. 8A and 8B now, in one embodiment, the planet-pivot-armassembly 410 can include a traction planet 332, a traction planet axle334, and pivot arms 380 having a slotted joint 1210. Theplanet-pivot-arm assembly 410 can also include skew rollers 1220, whichare rolling elements attached to each end of a pivot arm axle 334 andprovide for rolling contact of the traction planet axle 334 along skewsurfaces 910 of the input cage 352 and output cage 354. Theplanet-pivot-arm assembly 410 can include bearings 374. The skew rollers1220 and the bearings 374 can be supported by the traction planet axle334. The traction planet axle 334 passes through a bore formed in theradially outward end of a pivot arm 380.

In one embodiment, the pivot arms 380 are machined with a curvaturesuitable to axially translate the traction sun 333 in reaction to ashift mechanism input. The pivot arms 380 can be provide with a camsurface 1230. As will be further described below with reference to FIGS.13A-13D, the curvature of the cam surface 1230 can be configured toproduce a desired axial translation of the traction sun 333 duringshifting of the transmission ratio.

The traction planet axle 334 can be a generally cylindrical shaft thatextends through a bore formed through the center of the traction planet332. In some embodiments, the traction planet axle 334 interfaces withthe surface of the bore in the traction planet 332 via needle or radialbearings that align the traction planet 332 on the traction planet axle334. The traction planet axle 334 extends beyond the sides of thetraction planet 332 where the bore ends so that the pivot arms 380 canactuate a shift in the position of the traction planet 332. Where thetraction planet axle 334 extends beyond the edge of the traction planet332, it couples to the radial outward end of the pivot arms 380. Thetraction planet axle 334 passes through a bore formed in the radiallyoutward end of the pivot arms 380.

In various embodiments, the interface between the traction planets 332and the traction planet axles 334 can be any of the bearings describedin other patents or publications. In some embodiments, the tractionplanets 332 are fixed to, and rotate with, the planet axles 334. In theembodiment of FIG. 8A, the bearings 374 are positioned between thetraction planet axles 332 and the pivot arms 380 such that thetransverse forces acting on the traction planet axles 332 are reacted bythe pivot arms 380 as well as, or alternatively, the cage 356. In somesuch embodiments, the bearings 374 can be radial bearings (balls orneedles), journal bearings, or any other type of bearings or suitablemechanism.

Typically, traction-type transmissions use a clamping mechanism toprevent slippage between the traction planets 332 and the traction rings330, 336 when transmitting certain levels of torque. Provision of aclamping mechanism is sometimes referred to here as generating an axialforce, or providing an axial force generator. With reference to FIGS.4A-4D and 9, clamping force generation mechanisms that can be used withthe transmission 300 will now be described.

As mentioned above with reference to FIGS. 4A-4D, some embodiments ofthe transmission 300 preferably include an input load cam 328 and/or anoutput load cam 338. The following discussion of a load cam 700 appliesequally to both load cams 328, 338. In one embodiment, a load cam 700includes load cam rollers 705 and ramps 710, which can be formedintegral with a traction ring, such as input or output traction rings330 and 336. The rollers 705 can be supported and positioned in asuitable roller retainer, for example roller retainer 720. In someembodiments, a traction ring 330, 340 can includes about 16 ramps 710,with each ramp 710 having about a 10 degree incline. In certainembodiments, the ramps 710 are helical and have a lead equivalent toabout 55-66 mm over a 160-degree span. The input load cam 328 includesrollers 327 and ramps integral with the input traction ring 330, and theoutput load cam assembly 338 includes rollers 337 and ramps integralwith the output traction ring 336. The rollers 705, 327, 337 can bespherical, cylindrical, barreled, asymmetrical or other shape suitablefor a given application.

In some embodiments, the ramps 710 are provided on a ring that isfastened to the input driver 326 or to the input traction ring 330;alternatively, each of the input driver 326 and the input traction ringcan be fitted with rings having the ramps 710. In some embodiments, theinput traction ring 330 and the load cam assembly 328 are an integralunit, effectively as when the ramps 1610 are built into the inputtraction ring 330, and the rollers 705 and roller retainer 720 form adistinct assembly.

During operation of the transmission 300, the first stage planetary sungear 312 imparts torque to the input driver 326. The input driver 326transfers torque to the input traction ring 330 via the ramps 710, whichcan be integral with the input traction ring 330. As the input driver326 rotates, the ramps 710 activate the rollers 705, which ride up theramps 710. The rollers 705 wedge in place, pressed between the ramps 705and a surface of the input driver 326, and transmit both torque andaxial force through the ramps 705 from the input driver 326 to the inputtraction ring 330. The axial force then clamps the traction planets 332between the input traction ring 330, the output traction ring 336, andthe traction sun 333.

Turning to FIGS. 10A-10C now, an input driver 326 can be a generallycircular plate 552 with a central bore 554, which is adapted with aspline or other fastening device to engage the sun gear 312. The inputdriver 326 includes a surface 556 that engages the load cam rollers 327.The surface 556 can be flat or can have load cam ramps, such as theramps shown on the input traction ring 330 (see FIGS. 4B and 9, forexample). In one embodiment, the input driver 326 includes a bearingrace 558 that cooperates with the input bearing race 322 and the rollers324 to provide the functionality of a thrust bearing for supportingaxial loads and rolling contact between stationary and rotatingcomponents.

Referencing FIGS. 10D-10F now, an output driver 340 can be a generallycircular plate 560 having a central bore with a flange 562, which isadapted to receive bearings 395 and to engage with, for example, asprocket 348. In another embodiment, the flange 562 can be adapted toreceive a bearing 391 that locates and supports the output end cap 346.The output driver 340 includes a surface 564 that is configured toengage the load cam rollers 337. The surface 546 can be flat or can haveload ramps, such as the ramps shown (but not referenced) on the outputtraction ring 336. In one embodiment, the output driver 340 includes abearing race 566 that cooperates with the output bearing race 344 andthe rollers 342 to provide the functionality of a thrust bearing, asdiscussed above with reference to the input driver 326. The bearing race566 is located on a side of the output driver 326 that is opposite tothe side having the surface 564.

Referencing FIGS. 11A-12B now, the speed ratio of the transmission 300can be adjusted using the shift screw 370 and the shift pin hub 374. Inone embodiment, a shift wheel 375 can be used to drive the shift screw370. The shift wheel 375 can be, for example, a pulley or a compoundgear adapted to be actuated by a linear actuator such as a cable or achain (not shown). The housing 345 can be suitably adapted to allow thelinear actuator to access the shift wheel 375.

The shift pin hub 374 is coupled to the pivot arms 380 by shift pins(not shown) that fit in the fingers 376 and in the shift pin hole 1212of the pivot arms 380 (see FIGS. 8A-8B). The fingers 376 are configuredto fit in the slot 1280 of the pivot arms 380. The shift pin hub 374 isprovided with a threaded end 580, in one embodiment, to allow the shiftscrew 370 to actuate the shift pin hub 374 via corresponding shift screwthreads 1005 of the shift screw 370.

The shift screw 370 can mount coaxially with and is rotatable about thecentral shaft 360. In one embodiment, the shift screw 370 can be axiallyconstrained by the sun gear 312 and the ring gear 316. Suitable thrustbearings can be positioned between the shift screw 370 and,respectively, the sun gear 312 and the ring gear 316 (see FIG. 4B, forexample). In one embodiment, the shift screw 370 includes a shift screwflange 1010 adapted to couple to the shift wheel 375.

To adjust the speed ratio of the transmission 300, a shift input isprovided by the linear actuator (chain, cable, etc.) to the shift wheel375, which rotates the shift screw 370. The shift screw threads 1005engage the shift pin hub threads 580, and since the shift screw 370 isconstrained axially at the same time that the shift pin hub 374 isconstrained rotationally, the shift screw 370 causes the shift pin hub374 to move axially. The axial translation of the shift pin hub 374causes the pivot arms 380 to pivot on the pivot pins (not shown)coupling the shift pin hub fingers 376 and the pivot arms 380. The pivotarms 380 pivot about the centers of the planets 332. Because the pivotarms 380 are coupled to the traction planet axles 334, the pivoting ofthe pivot arms 380 causes the traction planet axles 334 to tilt radiallyinward or outward, which results in a change in the relative point ofcontact between the traction planets 332 and, respectively, the inputtraction ring 330 and the output traction ring 336. This change therelative point of contact between the traction planets 332 and thetraction rings 330, 336 results in a change in the speed ratio of thetransmission 300.

In some embodiments, it is preferable that the traction sun 333translate axially as the pivot arms 380 tilt the traction planet axles334. Translation of the traction sun 333 can be accomplished by atraction sun actuation device 382, which in one embodiment is positionedbetween the traction sun 333 and the pivot arms 380. In one embodiment,the traction sun actuation device 382 includes cam rollers 1805 adaptedto engage the cam surface 1230 of the pivot arms 380. The cam rollers1805 can be supported and positioned on cam roller support ring 1810having support extensions 1812. To react and transfer axial forces, anangular contact thrust bearing is positioned between the support ring1810 and the traction sun 333. In the embodiment illustrated in FIGS.13A-13D, a bearing race 1811 is integral with the support ring 1810, abearing race 1825 is suitably coupled or affixed to the traction sun333, and a set of bearing rollers 1820 is supported and positioned by abearing roller retainer 1815. In some embodiments, a traction sunactuation device 382 can be provided for each of end of the traction sun333, as illustrated in FIGS. 4A-4D.

As the pivot arms 380 pivot about the planets 332, the cam surface 1230of the pivot arms 380 acts on the cam rollers 1805, which transfer anaxial force to the cam roller support ring 1810. The cam rollers 1805are provided with flanges 1807 to engage the pivot arms 380, and therebythe support ring 1810 is constrained from rotation about the centralshaft 360. The support ring 1810 then transfers the axial force to thetraction sun 333 via the bearing race 1810, bearing rollers 1820, andbearing race 1825. As will be discussed further below, the curvature orprofile of the cam surface 1230 determines the relative speed betweenthe speed of axial translation of the traction sun 333 vis-à-vis thespeed of change of the tilt of the traction planet axles 334.

The profile of the shift cam surface 1230 usually varies according tothe location of the contact point between the traction sun 333 and thetraction planets 332, as well as the desired amount of relative axialmotion between the traction planets 332 and the traction sun 333. Theprofile of the cam surface 1230 can be such that axial translation ofthe traction sun 333 relative to the traction planets 332 isproportional to the change of the tilt of the traction planets axles334. The angle of tilt of the traction planet axles 334 is referred toherein as “gamma.” The applicant has discovered that controlling theaxial translation of the traction sun 333 relative to the change ingamma influences CVT ratio control forces. For example, if the axialtranslation of the traction sun 333 is linearly proportional to a changein gamma, the normal force at the cam surface 1230 and the cam roller1805 is generally parallel to the traction planet axles 334. Thisenables an efficient transfer of a shift moment about the tractionplanets 332 to horizontal shift forces that translate the traction sun333.

A linear relation between translation of the traction sun 333 and gammachange is given as translation of the traction sun 333 is themathematical product of the radius of the planets 332, the gamma angleand RSF (that is, translation of traction sun 333=ball radius*gammaangle*RSF), where RSF is a roll-slide factor. RSF describes thetransverse creep rate between the traction planets 332 and the tractionsun 333. As used here, “creep” is the discrete local motion of a bodyrelative to another. In traction drives, the transfer of power from adriving element to a driven element via a traction interface requirescreep. Usually, creep in the direction of power transfer is referred toas “creep in the rolling direction.” Sometimes the driving and drivenelements experience creep in a direction orthogonal to the powertransfer direction, in such a case this component of creep is referredto as “transverse creep.” During operation, the traction planet 332 andthe traction sun 333 on each other. When the traction sun 333 istranslated axially (that is, orthogonal to the rolling direction),transverse creep is imposed between the traction sun 333 and thetraction planets 332. An RSF equal to 1.0 indicates pure rolling. At RSFvalues less than 1.0, the traction sun 333 translates slower than thetraction planet 332 rotates. At RSF values greater than 1.0, thetraction sun 333 translates faster than the traction planet 332 rotates.

A process for defining a profile for the cam surface 1230 for anyvariation of transverse creep and/or location of the interface betweenthe traction sun 333 and the pivot arm 380 and cam roller 1805. Thisprocess generates different cam profiles and aids in determining theeffects on shift forces and shifter displacement. In one embodiment, theprocess involves the use of parametric equations to define atwo-dimensional datum curve that has the desired profile for the camsurface 1230. The curve is then used to generate models of the camsurface 1230. In one embodiment of the process, the parametric equationsof the datum curve are as follows:theta=2*GAMMA_MAX*t−GAMMA_MAXx=LEG*sin(theta)−0.5*BALL_DIA*RSF*theta*pi/180+0.5*ARM*cos(theta)y=LEG*cos(theta)−0.5*ARM*sin(theta)z=0

The angle theta varies from minimum gamma (which in some embodiments is−20 degrees) to maximum gamma (which in some embodiments is +20degrees). GAMMA_MAX is the maximum gamma. The parametric range variable“t” varies from 0 to 1. Here “x” and “y” are the center point of the camrollers 1805 on each side of the traction sun 333. The equations for xand y are parametric. “LEG” and “ARM” define the position of theinterface between the pivot arm 380, cam roller 1805, and traction sun333. More specifically, LEG is the perpendicular distance between thelongitudinal axis of the traction planet axle 334 to a line that passesthrough the centers of the two corresponding cam rollers 1805. ARM isthe distance between centers of the cam rollers 1805 on either side ofthe traction sun 333.

RSF values above zero are preferred. Applicant discovered that an RSF ofzero dramatically increases the force required to shift the CVT.Usually, RSF values above 1.0 and less than 2.5 are preferred. There isa maximum RSF for a maximum gamma angle. For example, for gamma equalsto +20 degrees an RSF of about 1.6 is the maximum. RSF further dependson the size of the traction planet 332 and the size of the traction sun333, as well as the location of the cam roller 1805.

Linear axial translation of the traction sun 333 relative to gamma isnot the only desired relation. Hence, for example, if it is desired thatthe translation of the traction sun 333 be linearly proportional to CVTratio, then the RSF factor is made a function of gamma angle or CVTratio so that the relation between the position of the traction sun 333and CVT ratio is linearly proportional. This is a desirable feature forsome types of control schemes.

It should be noted that while several embodiments have been describedabove that implement a continuously variable variator in conjunctionwith a planetary gear set for a bicycle transmission, in otherembodiments the planetary gear set is not used. Rather, the crankshaftcan be directly, or through a load cam assembly, coupled to the inputdriver 326 or the input traction ring 330 of the variator.

Turning to FIGS. 14A-14C now, a shift actuator 1 can be provided toactuate the shift wheel 375. As shown, the end cap 302 and/or theplanetary gearset carrier 320 can be adapted to allow the shift actuator1 to engage the shift wheel 375. The end cap 302 can have, for example,holes 2 that allow the shift actuator 1 to enter and exit the housing345. In one embodiment, the carrier 320 supports the shift wheel 375 (onan axle or pin that is not shown) and, hence, the carrier 320 can beprovided with holes 3 that allow the shift actuator 1 to pass into andout of the carrier 320 to access the shift wheel 375. The shift actuator1 can be, for example, a shift cable, wire, belt, etc. If the shiftwheel 375 is a gear with teeth, the shift actuator 1 can be a chain, forexample. It will be obvious to a person of ordinary skill in therelevant technology that other shift actuators can be used to controlthe shift wheel 375.

The foregoing description details certain embodiments of the invention.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the invention can be practiced in many ways.As is also stated above, it should be noted that the use of particularterminology when describing certain features or aspects of the inventionshould not be taken to imply that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated.

What we claim is:
 1. A continuously variable transmission forintegrating within a frame of a bicycle, comprising: a planetary gearset comprising a planet carrier coupled to a set of planet gears, theplanet carrier configured to receive a torque input from a set ofcranks, a fixed ring gear, and a sun gear, wherein rotation of theplanet gears drives the sun gear; and a variator, comprising an inputring coupled to the sun gear via an axial force generation mechanismcomprising a cam loader having a set of bearings in contact with a setof ramps, a plurality of tiltable traction planets arranged about acrankshaft of the bicycle, each tiltable traction planet in contact withthe input ring, an output ring, operationally coupled to the pluralityof traction planets, each tiltable traction planet in contact with theoutput ring, a cage, and an idler in contact with the plurality oftiltable traction planets.
 2. The continuously variable transmission ofclaim 1, wherein the output ring is integrated with a support structurefor the variator.
 3. The continuously variable transmission of claim 1,wherein the planet carrier is connected to the cage, and wherein torqueis supplied to the variator from the sun gear and the planet carrier. 4.The continuously variable transmission of claim 1, wherein the cage isfixed to the frame, and wherein torque is supplied to the variatorthrough the input ring.
 5. The continuously variable transmission ofclaim 1, wherein a housing of the continuously variable transmissionforms part of a bottom bracket.
 6. A bicycle, comprising: a plurality offrame members; a continuously variable transmission coupled to at leastone of the plurality of frame members, the continuously variabletransmission comprising a planetary gear set comprising a planet carriercoupled to a set of planet gears, the planet carrier configured toreceive a torque input from a set of cranks, a fixed ring gear, and asun gear, wherein rotation of the planet gears drives the sun gear; anda variator, comprising an input ring coupled to the sun gear via anaxial force generation mechanism comprising a cam loader having a set ofbearings in contact with a set of ramps, a plurality of tiltabletraction planets arranged about a crankshaft of the bicycle, eachtiltable traction planet in contact with the input ring, an output ringoperationally coupled to the plurality of traction planets, eachtiltable traction planet in contact with the output ring, a cage, and anidler in contact with the plurality of tiltable traction planets.
 7. Thebicycle of claim 6, wherein the output ring is integrated with a supportstructure for the variator.
 8. The bicycle of claim 6, wherein theplanet carrier is connected to the cage, and wherein torque is suppliedto the variator from the sun gear and the planet carrier.
 9. The bicycleof claim 6, wherein the cage is fixed to the frame, and wherein torqueis supplied to the variator through the input ring.
 10. The bicycle ofclaim 6, wherein a housing of the continuously variable transmissionforms part of a bottom bracket.